Location of a user device, associated with a cellular network, may be determined when the user device is used to place and/or receive a telephone call and/or a text message (e.g., a short message service (SMS) message). For example, a call details record (CDR) may be generated each time the user device is used to place or receive a telephone call and/or a text message. The CDR may identify a base station with which the user device communicates. An approximate location of the user device (e.g., within approximately 500 meters) may be determined based on the location of the base station and/or based on the location of other nearby base stations, such as using trilateration and/or triangulation techniques. This approximate location may be determined when a CDR is recorded.